Random access procedures for satellite communications

ABSTRACT

Systems and methods are disclosed for random access in a wireless communication system such as, e.g., a wireless communication system having a non-terrestrial (e.g., satellite-based) radio access network. Embodiments of a method performed by a wireless device and corresponding embodiments of a wireless device are disclosed. In some embodiments, a method performed by a wireless device for random access comprises performing an open-loop timing advance estimation procedure to thereby determine an open-loop timing advance estimate for an uplink between the wireless device and a base station. The method further comprises transmitting a random access preamble using the open-loop timing advance estimate. In this manner, random access can be performed even in the presence of a long propagation delay such as that present in a satellite-based radio access network. Embodiments of a method performed by a base station and corresponding embodiments of a base station are also disclosed.

RELATED APPLICATIONS

This application claims the benefit of provisional patent applicationSer. No. 62/717,359, filed Aug. 10, 2018, the disclosure of which ishereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to random access in a wirelesscommunications system that includes a non-terrestrial (e.g.,satellite-based) radio access network.

BACKGROUND

There is an ongoing resurgence of satellite communications. Severalplans for satellite networks have been announced in the past few years.The target services vary from backhaul and fixed wireless, totransportation, to outdoor mobile, to Internet of Things (IoT).Satellite networks could complement mobile networks on the ground byproviding connectivity to underserved areas and multicast/broadcastservices.

To benefit from the strong mobile ecosystem and economy of scale,adapting the terrestrial wireless access technologies including LongTerm Evolution (LTE) and New Radio (NR) for satellite networks isdrawing significant interest. For example, Third Generation PartnershipProject (3GPP) completed an initial study in Release 15 on adapting NRto support non-terrestrial networks, mainly satellite networks [1]. Thisinitial study focused on the channel model for the non-terrestrialnetworks, defining deployment scenarios, and identifying the keypotential impacts. 3GPP is conducting a follow-up study item in Release16 on solutions evaluation for NR to support non-terrestrial networks[2].

Satellite Communications

A satellite radio access network usually includes the followingcomponents:

-   -   a gateway that connects a satellite network to a core network,    -   a satellite that refers to a space-borne platform,    -   a terminal that refers to a User Equipment (UE),    -   a feeder link that refers to the link between a gateway and a        satellite, and    -   a service link that refers to the link between a satellite and a        terminal.

The link from the gateway to the terminal is often called a “forwardlink”, and the link from the terminal to the gateway is often called a“return link” or “access link.” Depending on the functionality of thesatellite in the system, two transponder options can be considered:

-   -   Bent pipe transponder: The satellite forwards the received        signal back to the earth with only amplification and a shift        from uplink frequency to downlink frequency.    -   Regenerative transponder: The satellite includes on-board        processing to demodulate and decode the received signal and        regenerate the signal before sending it back to the earth.

Depending on the orbit altitude, a satellite may be categorized as a LowEarth Orbit (LEO), Medium Earth Orbit (MEO), or Geostationary Orbit(GEO) satellite.

-   -   LEO: typical heights ranging from 500-1,500 kilometers (km),        with orbital periods ranging from 10-40 minutes.    -   MEO: typical heights ranging from 5,000-12,000 km, with orbital        periods ranging from 2-8 hours.    -   GEO: height at 35,786 km, with an orbital period of 24 hours.

A satellite typically generates several beams over a given area. Thefootprint of a beam is usually in an elliptical shape, which has beentraditionally considered as a cell. The footprint of a beam is alsooften referred to as a spotbeam. The footprint of a spotbeam may moveover the earth's surface with the satellite movement or may be earthfixed with some beam pointing mechanism used by the satellite tocompensate for its motion. The size of a spotbeam depends on the systemdesign, which may range from tens of kilometers to a few thousands ofkilometers.

FIG. 1 shows an example architecture of a satellite network with bentpipe transponders.

The two main physical phenomena that affect satellite communicationssystem design are the long propagation delay and Doppler effects. TheDoppler effects are especially pronounced for LEO satellites.

Propagation Delays

Propagation delay is a main physical phenomenon in a satellitecommunications system that makes the design different from that of aterrestrial mobile system. For a bent pipe satellite network, thefollowing delays are relevant:

-   -   One-way delay: The one-way delay is the delay from the Base        Station (BS) to the UE via the satellite, or the other way        around.    -   Round-trip delay: The round-trip delay is the delay from the BS        to the UE via the satellite and from the UE back to the BS via        the satellite.    -   Differential delay: The differential delay is the delay        difference of two selected points in the same spotbeam.        Note that there may be additional delay between the ground BS        antenna and the BS, which may or may not be collocated. This        delay depends on deployment. If the delay cannot be ignored, it        should be taken into account in the communications system        design.

The propagation delay depends on the length of the signal path, whichfurther depends on the elevation angles of the satellite seen by the BSand UE on the ground. The minimum elevation angle is typically more than10° for UE and more than 5° for BS on the ground. These values will beassumed in the delay analysis below.

The following Tables 1 and 2 are taken from 3GPP Technical Report (TR)38.811 [1]. As can be seen, the round-trip delay is much larger insatellite systems. For example, it is about 545 milliseconds (ms) for aGEO satellite system. In contrast, the round-trip time is normally nomore than 1 ms for typical terrestrial cellular networks.

TABLE 1 Propagation delays for GEO satellite at 35,786 km (extractedfrom Table 5.3.2.1-1 in 3GPP TR 38.811 [1]) GEO at 35786 km Elevationangle Path D (km) Time (ms) UE: 10° satellite-UE 40586 135.286 GW: 5°satellite-gateway 41126.6 137.088 90° satellite-UE 35786 119.286 BentPipe satellite One way delay Gateway-satellite_UE 81712.6 272.375 Roundtrip Time Twice 163425.3 544.751 Regenerative Satellite One way delaySatellite-UE 40586 135.286 Round Trip Time Satellite-UE-Satellite 81172270.572

TABLE 2 Propagation delays for NGSO satellites (extracted from Table5.3.4.1-1 in 3GPP TR 38.811 [1]) LEO at 600 km LEO at 1500 km MEO at10000 km Elevation Distance Delay Distance Delay Distance Delay anglePath D (km) (ms) D (km) (ms) D (km) (ms) UE: 10° satellite-UE 1932.246,440 3647.5 12,158 14018.16 46.727 GW: 5° satellite-gateway 2329.017.763 4101.6 13.672 14539.4 48.464 90° satellite-UE 600 2 1500 5 1000033.333 Bent pipe satellite One way 4261.2 14.204 7749.2 25.83 28557.695.192 delay Gateway-satellite UE Round Twice 8522.5 28.408 15498.451.661 57115.2 190.38 Trip Delay Regenerative satellite One waySatellite-UE 1932.24 6.44 3647.5 12.16 14018.16 46.73 delay RoundSatellite-UE-Satellite 3864.48 12.88 7295 24.32 28036.32 93.45 TripDelay

Generally, within a spotbeam covering one cell, the delay can be dividedinto a common delay component and a differential delay component. Thecommon delay is the same for all UEs in the cell and is determined withrespect to a reference point in the spotbeam. In contrast, thedifferential delay is different for different UEs which depends on thepropagation delay between the reference point and the point at which agiven UE is positioned within the spotbeam.

The differential delay is mainly due to the different path lengths ofthe access links, since the feeder link is normally the same forterminals in the same spotbeam. Further, the differential delay ismainly determined by the size of the spotbeam. It may range fromsub-millisecond for spotbeams on the order of tens of kilometers to tensof milliseconds for spotbeams on the order of thousands of kilometers.

Doppler Effects

Doppler is another major physical phenomenon that shall be properlytaken into account in a satellite communications system. The followingDoppler effects are particularly relevant:

-   -   Doppler shift: The Doppler shift is the shift of the signal        frequency due to the motion of the transmitter, the receiver, or        both.    -   Doppler variation rate: The Doppler variation rate is the        derivative of the Doppler shift function of time, i.e., it        characterizes how fast the Doppler shift evolves over time.        Doppler effects depend on the relative speed of the satellites        and the UE and the carrier frequency.

GEO satellites are fixed in principle and thus do not induce Dopplershift. In reality, however, they move around their nominal orbitalpositions due to, for example, perturbations. A GEO satellite istypically maintained inside a box [1]:

-   -   +/−37.5 km in both latitude and longitude directions        corresponding to an aperture angle of +/−0.05°    -   +/−17.5 km in the equatorial plane        The trajectory of the GEO satellite typically follows a figure        “8” pattern, as illustrated in FIG. 2. FIG. 2 illustrates        geostationary satellite trajectory (extracted from FIG.        5.3.2.3-2 in 3GPP TR 38.811 [1]).

Table 3 gives example Doppler shifts of GEO satellites. For a GEOsatellite maintained inside the box and moving according to the figure“8” pattern, we can see that the Doppler shifts due to the GEO satellitemovement are negligible.

If a GEO satellite is not maintained inside the box, the motion could benear GEO orbit with inclination up to 6°. The Doppler shifts due to theGEO satellite movement may not be negligible.

TABLE 3 Example Doppler shifts of GEO satellites (extracted from Tables5.3.2.3-4 and 5.3.2.3-5 in 3GPP TR 38.811 [1]) Frequency 2 GHz 20 GHz 30GHz S2 to S1 Doppler shift (Hz) −0.25 −2.4 −4.0 S1 to S4 Doppler shift(Hz) 2.25 22.5 34 Not maintained Doppler shift (Hz) 300 3000 4500 insidethe box (with inclination up to 6°)

The Doppler effects become remarkable for MEO and LEO satellites. Table4 gives example Doppler shifts and rates of Non-GEO (NGSO) satellites.We can see that the Doppler shifts and rates due to the NGSO satellitemovement should be properly considered in the communications systemdesign.

TABLE 4 Doppler shits and variation rates of NGSO satellites (extractedfrom Table 5.3.4.3.2-7 in 3GPP TR 38.811 [1]) Max Doppler Frequency MaxRelative shift (GHz) doppler Doppler variation 2 +/−48 kHz  0.0024% −544Hz/s LEO at 600 km 20 +/−480 kHz  0.0024% −5.44 kHz/s altitude 30 +/−720kHz  0.0024% −8.16 kHz/s 2 +/−40 kHz  0.002% −180 Hz/s LEO at 1500 km 20+/−400 kHz  0.002% −1.8 kHZ/s altitude 30 +/−600 kHz  0.002% −2.7 kHz/s2 +/−15 kHz 0.00075% −6 Hz/s MEO at 10000 km 20 +/−150 kHz 0.00075% −60Hz/s altitude 30 +/−225 kHz 0.00075% −90 Hz/s

Random Access Procedures in LTE and NR

The random access procedures in LTE and NR are similar. In the existingrandom access design, random access procedures serve multiple purposessuch as initial access when establishing a radio link, schedulingrequest, etc. Among others, an important objective of the random accessprocedures is to achieve uplink synchronization, which is important formaintaining the uplink orthogonality in LTE and NR. To preserve theorthogonality of uplink signals from different UEs in an OrthogonalFrequency Division Multiple Access (OFDMA) based system, the time ofarrival of each UE's signal needs to be within the Cyclic Prefix (CP) ofthe OFDM signal at the base station.

LTE and NR random access can be either contention-based orcontention-free. The contention-based random access procedure consistsof four steps, as illustrated in FIG. 3. These steps are: (1) the UEtransmits a random access preamble, which is also known as Msg1; (2) thenetwork transmits a Random Access Response (RAR), which is also known asMsg2, that contains a Timing Advance (TA) command and the scheduling ofuplink resources for the UE to use in the third step; (3) the UEtransmits its identity to the network using the scheduled resources in amessage known as Msg3; and (4) the network transmits a contentionresolution message (also referred to as Msg4) to resolve any contentiondue to multiple UEs transmitting the same random access preamble in thefirst step.

For contention-free random access, the UE uses reserved preamblesassigned by the BS. In this case, contention resolution is not needed,and thus only steps 1 and 2 are required.

Synchronization Signal (SS) Block Configuration

In NR, the set of Reference Signals (RSs) based on which UE performsinitial access is the SS/Physical Broadcast Channel Block (SSB). Thestructure of the SSB in NR is described below. The signals comprised inthe SSB may be used for measurements on an NR carrier, includingintra-frequency, inter-frequency, and inter-Radio Access Technology(RAT) (i.e., NR measurements from another RAT).

SSB (can also be referred to as SS/Physical Broadcast Channel (PBCH)block or SS block): NR Primary SS (NR-PSS), NR Secondary SS (NR-SSS),and/or NR-PBCH can be transmitted within an SSB. For a given frequencyband, an SSB corresponds to N Orthogonal Frequency Division Multiplexing(OFDM) symbols based on one subcarrier spacing (e.g., default orconfigured), and N is a constant. The UE is able to identify at leastOFDM symbol index, slot index in a radio frame, and radio frame numberfrom an SSB. A single set of possible SSB time locations (e.g., withrespect to radio frame or with respect to SS burst set) is specified perfrequency band. At least for the multi-beams case, at least the timeindex of SSB is indicated to the UE. The position(s) of actualtransmitted SSBs is informed for helping CONNECTED/IDLE modemeasurement, for helping a CONNECTED mode UE to receive downlinkdata/control in unused SSBs, and potentially for helping an IDLE mode UEto receive downlink data/control in unused SSBs. The maximum number ofSSBs within an SS burst set, L, for different frequency ranges are:

-   -   For frequency range up to 3 gigahertz (GHz), L is 4    -   For frequency range from 3 GHz to 6 GHz, L is 8    -   For frequency range from 6 GHz to 52.6 GHz, L is 64

SS burst set: One or multiple SS burst(s) further compose an SS burstset (or series) where the number of SS bursts within an SS burst set isfinite. From a physical layer specification perspective, at least oneperiodicity of SS burst set is supported. From a UE perspective, SSburst set transmission is periodic. At least for initial cell selection,the UE may assume a default periodicity of SS burst set transmission fora given carrier frequency (e.g., one of 5 ms, 10 ms, 20 ms, 40 ms, 80ms, or 160 ms). The UE may assume that a given SSB is repeated with a SSburst set periodicity. By default, the UE may neither assume the NewRadio BS (gNB) transmits the same number of physical beam(s) nor thesame physical beam(s) across different SSBs within an SS burst set. In aspecial case, an SS burst set may comprise one SS burst.

For each carrier, the SSBs may be time-aligned or overlap fully or atleast in part, or the beginning of the SSBs may be time-aligned (e.g.,when the actual number of transmitted SSBs is different in differentcells).

FIG. 4 illustrates an example configuration of SSBs, SS bursts, and SSburst sets/series.

Problems with Existing Solutions

There currently exist certain challenge(s). In particular, the design inthe existing random access procedures in LTE and NR is not suitable forsatellite communications systems.

SUMMARY

Systems and methods are disclosed for random access in a wirelesscommunication system such as, e.g., a wireless communication systemhaving a non-terrestrial radio access network (e.g., a satellite-basedradio access network). Embodiments of a method performed by a wirelessdevice and corresponding embodiments of a wireless device are disclosed.In some embodiments, a method performed by a wireless device for randomaccess comprises performing an open-loop timing advance estimationprocedure to thereby determine an open-loop timing advance estimate foran uplink between the wireless device and a base station. The methodfurther comprises transmitting a random access preamble using theopen-loop timing advance estimate. In this manner, random access can beperformed even in the presence of a long propagation delay such as thatpresent in a satellite-based radio access network.

In some embodiments, the method further comprises receiving, from thebase station, a random access response comprising a timing advance valueand determining a timing advance for the uplink between the wirelessdevice and the base station based on the timing advance value comprisedin the random access response and the open-loop timing advance estimate.In some embodiments, the random access response schedules resources foran uplink transmission from the wireless device, and the method furthercomprises transmitting an uplink transmission to the base station usingthe scheduled resources and the determined timing advance, wherein theuplink transmission comprises an identity of the wireless device and anindication of the open-loop timing advance estimate. In someembodiments, the indication of the open-loop timing advance estimate isthe open-loop timing advance estimate. In some other embodiments, theindication of the open-loop timing advance estimate is a differentialvalue that equals a difference between the open-loop timing advanceestimate and a predefined or preconfigured reference value.

In some embodiments, the random access preamble is a function of theopen-loop timing advance estimate. In some embodiments, the methodfurther comprises selecting the random access preamble from a subgroupof a plurality of possibly random access preambles, the subgroup beingchosen based on the open-loop timing advance estimate. In someembodiments, the random access preamble provides an indication of theopen-loop timing advance estimate. In some embodiments, the methodfurther comprises receiving, from the base station, a random accessresponse comprising a timing advance value and determining a timingadvance for the uplink between the wireless device and the base stationbased on the timing advance value comprised in the random accessresponse and the open-loop timing advance estimate. In some embodiments,the random access response schedules resources for an uplinktransmission from the wireless device, and the method further comprisestransmitting an uplink transmission to the base station using thescheduled resources and the determined timing advance, the uplinktransmission comprising an identity of the wireless device andinformation that, together with a random access preamble transmitted bythe wireless device, provide an indication of the open-loop timingadvance estimate.

In some embodiments, the base station is part of a satellite radioaccess network comprising a satellite and a gateway that communicativelycouples the base station to the satellite.

In some embodiments, a method performed by a wireless device for randomaccess in a radio access network comprises transmitting a random accesspreamble and receiving, from a base station, a random access responsecomprising a timing advance value, the timing advance value beinggreater than 2 milliseconds (ms). In some embodiments, the timingadvance value is greater than 10 ms. In some other embodiments, thetiming advance value is greater than 50 ms. In some other embodiments,the timing advance value is greater than 100 ms.

In some embodiments, the timing advance value is within a range ofT_(min) to T_(max), wherein T_(min) and/or T_(max) are a function of adeployment of the radio access network.

In some embodiments, the base station is part of a satellite radioaccess network comprising a satellite and a gateway that communicativelycouples the base station to the satellite. In some embodiments, thetiming advance value is within a range of T_(min) to T_(max), whereinT_(min) and/or T_(max) are a function of whether the satellite is a LowEarth Orbit (LEO), Medium Earth Orbit (MEO), or Geostationary Orbit(GEO) satellite.

In some embodiments, the method further comprises adjusting a timingadvance of the wireless device based on the timing advance valuecomprised in the random access response and transmitting an uplinktransmission to the base station using the timing advance.

In some embodiments, the method further comprises adjusting a timingadvance of the wireless device based on the timing advance valuecomprised in the random access response and a configured referencetiming and transmitting an uplink transmission to the base station usingthe timing advance.

In some embodiments, a method performed by a wireless device for randomaccess in a radio access network comprises receiving, from a basestation, a reference timing advance, the reference timing advance beingbased on a largest or smallest possible round-trip signal delay in aservice area of the base station and transmitting a random accesspreamble using a timing advance that is equal to the reference timingadvance.

In some embodiments, the method further comprises receiving, from a basestation, a random access response comprising information that, togetherwith the reference timing advance, indicates a timing advance value forthe wireless device. In some embodiments, the information comprises anumber of slots and a fraction of a slot. In some embodiments, therandom access response further comprises a random access channelidentifier that indicates the random access preamble and a subframe overwhich the random access preamble was received by the base station. Insome embodiments, the method further comprises determining that therandom access channel identifier matches the random access preambletransmitted by the wireless device and, upon determining that the randomaccess channel identifier matches the random access preamble transmittedby the wireless device, transmitting an uplink transmission using thetiming advance value indicated by the information comprised in therandom access response.

In some embodiments, the base station is part of a satellite radioaccess network comprising a satellite and a gateway that communicativelycouples the base station to the satellite.

In some embodiments, a method performed by a wireless device for randomaccess in a radio access network comprises transmitting a random accesspreamble and receiving, from a base station, a random access responsecomprising a timing advance value for subframe boundary alignment.

In some embodiments, the timing advance value is one of a range ofpossible timing advance values, the range of possible timing advancevalues being −0.5 ms to 0.5 ms. In some other embodiments, the timingadvance value is one of a range of possible timing advance values, therange of possible timing advance values being 0 ms to 1.0 ms.

In some embodiments, the method further comprises transmitting, to thebase station, an indication that the wireless device is capable ofperforming open-loop timing advance estimation. In some embodiments, themethod further comprises transmitting, to the base station, anindication that the wireless device is capable of estimating propagationdelay, differential delay, or both propagation delay and differentialdelay. In some embodiments, the indication is transmitted during randomaccess or outside of random access.

In some embodiments, the base station is part of a satellite radioaccess network comprising a satellite and a gateway that communicativelycouples the base station to the satellite.

In some embodiments, a method performed by a wireless device for randomaccess in a radio access network comprises transmitting an indication toa base station that the wireless device is capable of performingopen-loop timing advance estimation. In some embodiments, the basestation is part of a satellite radio access network comprising asatellite and a gateway that communicatively couples the base station tothe satellite.

In some embodiments, a method performed by a wireless device for randomaccess in a radio access network comprises transmitting a random accesspreamble, receiving, from a base station, a random access responsecomprising information that indicates a processing latency at the basestation between reception of the random access preamble by the basestation and transmission of the random access response by the basestation, and estimating a round-trip propagation delay of the wirelessdevice by subtracting the processing latency at the base station from atime duration between transmission of the random access preamble at thewireless device and receiving the random access response at the wirelessdevice.

In some embodiments, the random access response further comprises anextended timing advance value. In some embodiments, the extended timingadvance value is from a range of possible extended timing advance valuesof −0.5 ms to 0.5 ms.

In some embodiments, random access preambles are divided into N preamblegroups each assigned one subframe to provide a subframe pattern that isrepeated every M subframes where M≥N, and the method further comprisesobtaining system information comprising N, M, and a reference timingvalue, selecting the random access preamble from one of the N preamblegroups that corresponds to a subframe in which the random accesspreamble is to be transmitted, and selecting a random access radionetwork temporary identifier, the random access radio network temporaryidentifier being a function of the one of the N preamble groups fromwhich the random access preamble was selected and M. Transmitting therandom access preamble comprises transmitting the random access preamblein the subframe that corresponds to the one of the N preamble groupsfrom which the random access preamble was selected.

In some embodiments, the base station is part of a satellite radioaccess network comprising a satellite and a gateway that communicativelycouples the base station to the satellite.

In some embodiments, a wireless device for performing random access in aradio access network is adapted to perform any one of the embodiments ofthe method of operation of a wireless device described above. In someembodiments, the wireless device comprises one or more transmitters, oneor more receivers, and processing circuitry associated with the one ormore transmitters and the one or more receivers, wherein the processingcircuitry configured to cause the wireless device to perform any one ofthe embodiments of the method of operation of a wireless devicedescribed above.

Embodiments of a method performed by a base station and correspondingembodiments of a base station are also disclosed. In some embodiments, amethod performed by a base station for enabling random access in a radioaccess network comprises detecting a random access preamble from awireless device, transmitting a random access response comprising atiming advance value, and receiving, from the wireless device, an uplinktransmission, wherein the uplink transmission comprises an identity ofthe wireless device and an indication of an open-loop timing advanceestimate utilized by the wireless device to transmit the random accesspreamble. In some embodiments, the base station is part of a satelliteradio access network comprising a satellite and a gateway thatcommunicatively couples the base station to the satellite.

In some embodiments, a method performed by a base station for enablingrandom access in a radio access network comprises detecting a randomaccess preamble from a wireless device, the random access preamble beinga function of an open-loop timing advance estimate of the wirelessdevice and transmitting, to the wireless device, a random accessresponse comprising a timing advance value.

In some embodiments, the random access preamble is from a subgroup of aplurality of possibly random access preambles, the subgroup beingindicative of the open-loop timing advance estimate.

In some embodiments, the random access preamble provides an indicationof the open-loop timing advance estimate.

In some embodiments, the method further comprises receiving, from thewireless device, an uplink transmission comprising an identity of thewireless device and information that, together with the random accesspreamble transmitted by the wireless device, provide an indication ofthe open-loop timing advance estimate.

In some embodiments, the base station is part of a satellite radioaccess network comprising a satellite and a gateway that communicativelycouples the base station to the satellite.

In some embodiments, a method performed by a base station for enablingrandom access in a radio access network comprises detecting a randomaccess preamble from a wireless device and transmitting, to the wirelessdevice, a random access response comprising a timing advance value, thetiming advance value being greater than 2 ms.

In some embodiments, the timing advance value is greater than 10 ms. Insome embodiments, the timing advance value is greater than 50 ms. Insome embodiments, the timing advance value is greater than 100 ms.

In some embodiments, the timing advance value is within a range ofT_(min) to T_(max), wherein T_(min) and/or T_(max) are a function of adeployment of the radio access network.

In some embodiments, the base station is part of a satellite radioaccess network comprising a satellite and a gateway that communicativelycouples the base station to the satellite. In some embodiments, thetiming advance value is within a range of T_(min) to T_(max), whereinT_(min) and/or T_(max) are a function of whether the satellite is a LEO,MEO, or GEO satellite.

In some embodiments, a method performed by a base station for enablingrandom access in a radio access network comprises transmitting, to oneor more wireless devices, a reference timing advance, wherein thereference timing advance is based on a largest or smallest possibleround-trip signal delay in a service area of the base station. Themethod further comprises detecting a random access preamble from awireless device and transmitting, to the wireless device, a randomaccess response comprising information that, together with the referencetiming advance, indicates a timing advance value for the wirelessdevice. In some embodiments, detecting the random access preamble fromthe wireless device comprise detecting the random access preamble fromthe wireless device within a time window that covers the largest andsmallest possible round-trip signal delay in the service area, and themethod further comprises, based on the detected random access preamble,determining the timing advance value for the detected random accesspreamble using a start of a last or first subframe in the time window asa timing reference. In some embodiments, the information comprises anumber of slots and a fraction of a slot.

In some embodiments, the random access response further comprises arandom access channel identifier that indicates the random accesspreamble and a subframe over which the random access preamble wasreceived by the base station.

In some embodiments, the base station is part of a satellite radioaccess network comprising a satellite and a gateway that communicativelycouples the base station to the satellite.

In some embodiments, a method performed by a base station for enablingrandom access in a radio access network comprises detecting a randomaccess preamble from a wireless device and transmitting, to the wirelessdevice, a random access response comprising a timing advance value forsubframe boundary alignment.

In some embodiments, the timing advance value is one of a range ofpossible timing advance values, the range of possible timing advancevalues being −0.5 ms to 0.5 ms. In some other embodiments, the timingadvance value is one of a range of possible timing advance values, therange of possible timing advance values being 0 ms to 1.0 ms.

In some embodiments, the method further comprises receiving, from thewireless device, an indication that the wireless device is capable ofperforming open-loop timing advance estimation. In some embodiments, theindication is received during random access or outside of random access.

In some embodiments, the base station is part of a satellite radioaccess network comprising a satellite and a gateway that communicativelycouples the base station to the satellite.

In some embodiments, a method performed by a base station for enablingrandom access in a radio access network comprises receiving, from awireless device, an indication that the wireless device is capable ofperforming open-loop timing advance estimation. In some embodiments, thebase station is part of a satellite radio access network comprising asatellite and a gateway that communicatively couples the base station tothe satellite.

In some embodiments, a method performed by a base station for enablingrandom access in a radio access network comprises detecting a randomaccess preamble from a wireless device and transmitting, to the wirelessdevice, a random access response comprising information that indicates aprocessing latency at the base station between reception of the randomaccess preamble by the base station and transmission of the randomaccess response by the base station.

In some embodiments, the random access response further comprises anextended timing advance value. In some embodiments, the extended timingadvance value is from a range of possible extended timing advance valuesof −0.5 ms to 0.5 ms.

In some embodiments, random access preambles are divided into N preamblegroups each assigned one subframe to provide a subframe pattern that isrepeated every M subframes where M≥N, and the method further comprisesproviding, to the wireless device, system information comprising N, M,and a reference timing value. Further, the random access preamble isfrom one of the N preamble groups that corresponds to a subframe inwhich the random access preamble is detected, and a random access radionetwork temporary identifier associated with the random access preambleis a function of the one of the N preamble groups from which the randomaccess preamble was selected and M.

In some embodiments, the base station is part of a satellite radioaccess network comprising a satellite and a gateway that communicativelycouples the base station to the satellite.

In some embodiments, a base station for enabling random access in aradio access network is adapted to perform any one of the embodiments ofthe method performed by a base station described above. In someembodiments, the base station comprises processing circuitry configuredto cause the base station to perform any one of the embodiments of themethod performed by a base station described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the disclosure, andtogether with the description serve to explain the principles of thedisclosure.

FIG. 1 shows an example architecture of a satellite network with bentpipe transponders;

FIG. 2 illustrates geostationary satellite trajectory;

FIG. 3 illustrates a contention-based random access procedure;

FIG. 4 illustrates an example configuration of Synchronization SignalBlocks (SSBs), Synchronization Signal (SS) bursts, and SS burstsets/series;

FIG. 5 illustrates a flow chart of a random access procedure from theperspective of a User Equipment (UE) in accordance with a firstembodiment of the present disclosure;

FIG. 6 further illustrates an example of how the UE adjusts its uplinktiming first based on an open-loop estimate and later fine tunes itsuplink timing based on the command from the base station in accordancewith the first embodiment of the present disclosure;

FIG. 7 is a flow chart that illustrates a random access procedure fromthe perspective of a base station in accordance with the firstembodiment of the present disclosure;

FIG. 8 illustrates a flow chart of a random access procedure from theperspective of a UE in accordance with a second embodiment of thepresent disclosure;

FIG. 9 is a flow chart that illustrates a random access procedure fromthe perspective of a base station in accordance with the secondembodiment of the present disclosure;

FIG. 10 illustrates a flow chart of a random access procedure from theperspective of a UE in accordance with a third embodiment of the presentdisclosure;

FIG. 11 further illustrates an example of how the UE adjusts its uplinktiming based on the command from the base station in accordance with thethird embodiment of the present disclosure;

FIG. 12 is a flow chart that illustrates a random access procedure fromthe perspective of a base station in accordance with the thirdembodiment of the present disclosure;

FIG. 13 illustrates the operation of a UE and a base station inaccordance with another embodiment of the present disclosure;

FIG. 14 illustrates a flow chart of a random access procedure from theperspective of a UE in accordance with a fourth embodiment of thepresent disclosure;

FIG. 15 further illustrates an example of how the UE adjusts its uplinktiming based on the command from the base station in accordance with thefourth embodiment of the present disclosure;

FIG. 16 is a flow chart that illustrates a random access procedure fromthe perspective of a base station in accordance with the fourthembodiment of the present disclosure;

FIG. 17 illustrates the operation of a UE and a base station inaccordance with one example of a fifth embodiment of the presentdisclosure;

FIGS. 18 through 20 illustrate example embodiments of a radio accessnode (e.g., a base station);

FIGS. 21 and 22 illustrate example embodiments of a UE;

FIG. 23 illustrate an example of a communication system in whichembodiments of the present disclosure may be implemented;

FIG. 24 illustrates example implementations of the host computer, basestation, and UE of FIG. 23;

FIGS. 25 through 28 are flow charts that illustrate example methodsimplemented in a communication system.

DETAILED DESCRIPTION

The embodiments set forth below represent information to enable thoseskilled in the art to practice the embodiments and illustrate the bestmode of practicing the embodiments. Upon reading the followingdescription in light of the accompanying drawing figures, those skilledin the art will understand the concepts of the disclosure and willrecognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure.

Radio Node: As used herein, a “radio node” is either a radio access nodeor a wireless device.

Radio Access Node: As used herein, a “radio access node” or “radionetwork node” is any node in a radio access network of a cellularcommunications network that operates to wirelessly transmit and/orreceive signals. Some examples of a radio access node include, but arenot limited to, a base station (e.g., a New Radio (NR) base station(gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation(5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP LongTerm Evolution (LTE) network), a high-power or macro base station, alow-power base station (e.g., a micro base station, a pico base station,a home eNB, or the like), and a relay node.

Core Network Node: As used herein, a “core network node” is any type ofnode in a core network. Some examples of a core network node include,e.g., a Mobility Management Entity (MME), a Packet Data Network Gateway(P-GW), a Service Capability Exposure Function (SCEF), or the like.

Wireless Device: As used herein, a “wireless device” is any type ofdevice that has access to (i.e., is served by) a cellular communicationsnetwork by wirelessly transmitting and/or receiving signals to a radioaccess node(s). Some examples of a wireless device include, but are notlimited to, a User Equipment (UE) in a 3GPP network and a Machine TypeCommunication (MTC) device.

Network Node: As used herein, a “network node” is any node that iseither part of the radio access network or the core network of acellular communications network/system.

Note that the description given herein focuses on a 3GPP cellularcommunications system and, as such, 3GPP terminology or terminologysimilar to 3GPP terminology is oftentimes used. However, the conceptsdisclosed herein are not limited to a 3GPP system.

Note that, in the description herein, reference may be made to the term“cell;” however, particularly with respect to 5G NR concepts, beams maybe used instead of cells and, as such, it is important to note that theconcepts described herein are equally applicable to both cells andbeams.

In the embodiments below, when it is stated that “BS configures . . . ”,we mean that the Base Station (BS) configures the corresponding subjectsin the system information.

As discussed above, the design in the existing random access proceduresin LTE and NR is not suitable for satellite communications systems. Inparticular, the timing relationship is based on the terrestrialpropagation radio environment, where the round-trip delay is usuallywithin 1 millisecond (ms). As a result, it cannot handle the longpropagation delays in satellite communications systems that range fromtens of milliseconds (Low Earth Orbit (LEO)) to hundreds of milliseconds(Geostationary Orbit (GEO)), and the large differential delay in aspotbeam in satellite communications systems that may range fromsub-milliseconds to tens of milliseconds (depending on the size ofspotbeam).

Certain aspects of the present disclosure and their embodiments mayprovide solutions to the aforementioned or other challenges. In thisdisclosure, systems and methods are disclosed for adapting random accessprocedures in LTE and NR for satellite networks.

The proposed solutions for random access procedures consider both thecase when UE can perform open-loop timing estimation and the case whenthe base station utilizes implementation-based solutions to estimate thelong propagation delay and/or large differential delay.

In some embodiments, methods are disclosed for adapting random accessprocedures currently designed for terrestrial networks to deal with thelong propagation delay that exists in, for example, satellitecommunications systems.

Some non-limiting examples of embodiments disclosed herein are asfollows:

-   -   Embodiment 1: A method of a random access procedure where the UE        performs open-loop Timing Advance (TA) estimation and applies        the estimated TA before sending a random access preamble in        Msg1; further adjusts TA based on closed-loop feedback from the        BS in Msg2; and informs the BS about its open-loop timing        estimate in Msg3.    -   Embodiment 2: A method of a random access procedure where the UE        performs open-loop TA estimation and applies the estimated TA        before sending a random access preamble in Msg1; chooses a TA        dependent Physical Random Access Channel (PRACH) transmission        resource in a subframe based on an open-loop timing estimate to        send Msg1; further adjusts TA based on closed-loop feedback from        the BS in Msg2; and informs the BS about its remaining        information on the open-loop timing estimate in Msg3 if the        information is not completely carried by the selection of the        transmission resource in Msg1.    -   Embodiment 3: A method of a random access procedure where the UE        performs TA by combining the timing information broadcast in        System Information (SI) and TA command transmitted in Msg2.    -   Embodiment 4: A method of a random access procedure where the UE        indicates its open-loop timing estimate capability to the        network.    -   Embodiment 5: A method of a random access procedure where the BS        indicates to the UE its processing latency between the reception        time of Msg1 at the BS and the transmission time of Msg2 at the        BS; the UE estimates its round-trip propagation delay by        subtracting the BS processing latency from the time duration        between the transmission time of Msg1 at the UE and the        reception time of Msg2 at the UE.

Certain embodiments may provide one or more of the following technicaladvantage(s). The proposed solutions for a random access procedure dealwith the core physical phenomenon of long propagation delay in satellitecommunications systems. The solutions are key for adapting LTE and NRfor satellite networks.

The embodiments of the UE and BS as well as the embodiments of themethod of operation thereof described herein may be implemented in anysuitable type of wireless communication system such as, e.g., a cellularcommunications network including a satellite radio access network 100such as that illustrated in FIG. 1. As illustrated in FIG. 1, thesatellite radio access network 100 includes a satellite 102 (i.e., aspace or airborne radio access node or platform), one or more gateways104 that interconnect the satellite 102 to a core network 106, and/or aland-based BS component 108. The functionality of the BS describedherein may be implemented in the satellite 102 or distributed betweenthe satellite 102 and a land-based BS component 108 connected to thesatellite 102 via the gateway 104 (e.g., the satellite 102 may implementL1 functionality and the land-based BS component 108 may implement L2and L3 functionality). A UE 110 communicates with the satellite radioaccess network 100 via the satellite 102. The functionality of a UE asdescribed herein may be implemented in the UE 110.

Embodiment 1

A UE performs an open-loop TA estimate. The UE applies TA using theopen-loop TA estimate before sending Msg1 in the random accessprocedure. A BS sends back a closed-loop timing adjustment command inMsg2. This command includes a TA value. The UE adjusts its TA based onthe command received in Msg2 before sending Msg3 to the BS. The UEincludes its open-loop timing estimate in Msg3 to facilitate BSscheduling henceforth.

FIG. 5 illustrates a flow chart of the random access procedure from theUE perspective. As illustrated, the UE reads a random accessconfiguration from system information (step 500). The UE also performsopen-loop timing estimation and adjusts its TA based on the resultingopen loop-timing estimate (step 502). The UE transmits a random accesspreamble (i.e., Msg1) in accordance with the random accessconfiguration, using the adjusted TA (which is based on the open-looptiming estimate) (step 504). The UE subsequently receives a randomaccess response (i.e., Msg2) from the radio access network and furtheradjusts it TA based on the closed-loop timing adjustment commandreceived in Msg2 (step 506). The UE then transmits Msg3 (step 508). InEmbodiment 1, the UE includes its open-loop timing estimate in Msg3. Inscenarios where contention resolution is performed, the UE receives Msg4(step 510).

FIG. 6 further illustrates how the UE adjusts its uplink timing firstbased on an open-loop estimate and later fine tunes its uplink timingbased on the command from the BS. In particular, FIG. 6 illustratestiming relationships for Embodiments 1 and 2.

Next, a few non-limiting examples are given to describe how some of thesteps may be implemented:

-   -   Open-loop TA estimate (applicable to all embodiments): In one        example, the UE uses Global Positioning System (GPS) information        regarding the UE (i.e., terminal) position and satellite        ephemeris data. In another example, the system frame timing may        be pre-specified so that the start time of each system frame is        known to the UE. For example, it may be specified that the start        time of system frame 0 is every T seconds (e.g., T=10 seconds)        starting from a certain date and time, for instance starting        from 2019-01-01 00:00:00. The UE can estimate its one way delay        to a BS by comparing the time a downlink system subframe is        received at the UE and the expected start time of the system        frame. In another example, one-way propagation delay is derived        when the network broadcasts a fine granularity GPS time (without        TA compensation and with a granularity of 1 microsecond (μs)) as        introduced in System Information Block 16 (SIB-16) in LTE        Release 15 and by comparing the received GPS time from the        network and the UE's knowledge of the actual GPS time from GPS        information.    -   A separate PRACH resource (in time, frequency, space, and/or        code) may be configured for the UE to transmit Msg1 in this        random access process.        -   Random Access Radio Network Temporary Identifier (RA-RNTI)            used for Msg2 Physical Downlink Control Channel (PDCCH)            scrambling is set according to time after applying the TA at            the UE    -   A new range for TA command in Msg2 may be defined.        -   Example 1: Shift the existing unipolar TA range [0, Tmax] to            a bipolar TA range [−Tmax/2, Tmax/2]. The same number of TA            bits can be used. In this example, it is assumed that a UE            is able to estimate its open-loop TA at least within a            fraction of Tmax/2.        -   Example 2: Define a new TA range [−T1, T2] where T1 and T2            are positive values, and choose the number of TA bits            accordingly.    -   Timing reporting in Msg3        -   Example 1: The UE reports the absolute open-loop timing            estimate, either in units of a fraction of a slot or in a            slot or both.        -   Example 2: The UE reports the differential value that equals            the absolute open-loop timing estimate minus a reference            timing value.            -   The reference timing value may be broadcast in SI.            -   Different reference timing value ranges may be defined                for different satellite deployments (for example LEO,                Medium Earth Orbit (MEO), and GEO can have different                reference timing value ranges).            -   The BS may choose the reference timing based on, for                example:                -   a point in a cell footprint or an Synchronization                    Signal (SS)/Physical Broadcast Channel Block (SSB)                    beam footprint on the Earth's surface that has the                    shortest or longest propagation delay, or                -   the center of a cell footprint or an SSB beam                    footprint on the Earth's surface.            -   In some embodiments, the reference timing value is                chosen equal to the common delay component associated                with a spotbeam.    -   Scheduling of Msg3        -   The BS may schedule Msg3 based on the largest propagation            delay in a cell footprint or an SSB beam footprint on the            Earth's surface, if the BS does not know the UE's            propagation delay already.    -   Key SI (applicable to all embodiments)        -   As mentioned above, the reference timing value may be            broadcast in SI, for example in SIB2.            -   A reference timing value may be broadcast per cell; or            -   A reference timing value may be broadcast per SSB beam.        -   Two options to indicate to the UE whether the UE reports            absolute open loop timing estimate (Example 1) or            differential value (Example 2) are as follows.            -   Option 1: If the reference timing value is present in                SI, the UE reports according to Example 2 and, if the                reference value is not present in SI, the UE reports                according to Example 1.            -   Option 2: In addition to the reference value being                present in SI, there may be a bit indicating to the UE                whether absolute or differential timing reporting should                be applied.

FIG. 7 is a flow chart that illustrates the random access procedure ofEmbodiment 1 from the BS perspective. As illustrated, the BS broadcastsSI including a random access configuration (step 700). The BS receivesMsg1 from the UE (step 702). As discussed above, the UE performsopen-loop timing estimation uses the resulting open-loop timing estimateto transmit Msg1. The BS detects Msg1 and transmits Msg2, where Msg2includes a closed-loop timing adjustment command (step 704). The BS thenreceives Msg3 from the UE (step 706). In Embodiment 1, Msg3 includesinformation that indicates the open-loop timing estimate of the UE. Inscenarios where contention resolution is performed, the BS transmitsMsg4 (step 708).

Embodiment 2

A UE performs an open-loop TA estimate. The UE applies TA using theopen-loop timing estimate before sending Msg1. Msg1 carries theinformation on the UE open-loop timing estimate. This is achieved byfurther dividing each current group of PRACH resources into subgroups,with each subgroup corresponding to a timing range. The UE selects thePRACH preamble from the subgroup that corresponds to its open-looptiming estimate and transmits Msg1. The BS sends back a closed-looptiming adjustment command in Msg2. The UE adjusts its TA based on thecommand in Msg2 before sending Msg3.

Compared to Embodiment 1 where the UE's open-loop timing estimateinformation is carried in Msg3, Embodiment 2 allows the UE to indicateits open-loop timing estimate information in Msg1. FIG. 8 illustrates aflow chart of a random access procedure from the UE perspective. How theUE adjusts its uplink timing first based on an open-loop estimate andlater tunes it based on the command from the BS is similar to inEmbodiment 1, as illustrated in FIG. 5. As illustrated in FIG. 8, the UEreads a random access configuration from SI (step 800). The UE alsoperforms open-loop timing estimation and adjusts its TA based on theresulting open-loop timing estimate (step 802). The UE selects a randomaccess preamble based on the open-loop timing estimate, and transmitsthe random access preamble (i.e., Msg1) in accordance with the randomaccess configuration, using the adjusted TA (which is based on theopen-loop timing estimate) (step 804). As discussed above, the UEselects the random access preamble from a subgroup of PRACH resourcesthat corresponding to a timing range in which its open-loop timingestimate falls. The UE subsequently receives a Random Access Response(RAR) (i.e., Msg2) from the radio access network and further adjusts itTA based on the closed-loop timing adjustment command received in Msg2(step 806). The UE then transmits Msg3 (step 808). In scenarios wherecontention resolution is performed, the UE receives Msg4 (step 810).

Next, a few non-limiting examples are given to describe how some of thesteps may be implemented.

-   -   A separate PRACH resource (in time, frequency, space, and/or        code) may be configured for the UE to transmit Msg1 in this        random access process.    -   Each group of the PRACH resource is divided into N configurable        groups: group 0, . . . , N−1. Group i is used for the UE with        the open-loop timing estimate belonging to the i-th group.        -   Example 1: The BS configures N+1 break time points T₀, T₁, .            . . , T_(N). Group i is used for the UE with the open-loop            timing estimate in the range [T_(i), T_(i+1)).            -   Example 1a: The UE selects the group based on the                differential value that equals the absolute open-loop                timing estimate minus a reference timing value broadcast                in SI. Group i is used for the UE with the differential                timing value in the range [T_(i), T_(i+1)).        -   Example 2: The BS configures T_(min) and step size Δ. Group            i is used for the UE with open-loop timing estimate in the            range [T_(min)+(i−1)*Δ, T_(min)+i*Δ), for i=1, . . . , N−1,            and [T_(min)+N*Δ, +∞) for i=N.            -   Example 2a: The UE selects the group based on the                differential value that equals the absolute open-loop                timing estimate minus a reference timing value broadcast                in SI. Group i is used for the UE with the differential                timing value in the range [T_(min)+(i−1)*Δ,                T_(min)+i*Δ), for i=1, . . . , N−1, and [T_(min)+N*Δ,                +∞) for i=N.                -   Example 2a-1: T_(min) can be fixed to 0, and Δ can                    be fixed to 1 ms in the specification. The BS                    configures N. For example, for a spotbeam with a                    maximum differential delay of 15.5 ms, the BS                    configures N=16, and PRACH group i is used for the                    UE with the differential timing value in the range                    [i−1, i) ms for i=1, . . . , 15, and [15, +∞) for                    i=16.    -   A new range for TA command in Msg2 may be defined        -   Example 1: Shift the existing unipolar TA range [0, Tmax] to            a bipolar TA range [−Tmax/2, Tmax/2]. The same number of TA            bits can be used.        -   Example 2: Define a new TA range [−T1, T2] where T1 and T2            are positive values, and choose the number of TA bits and            the mapping of a bit string to a TA value accordingly.

Note that the description up until now assumes the open-loop timing iscommunicated from the UE to the BS in Msg3 in Embodiment 1 and in Msg1in Embodiment 2. A combination of Embodiments 1 and 2 is possible: partof the open-loop timing information is indicated in Msg1 and the rest inMsg3. For example, the most significant bits of the timing informationmay be conveyed in Msg1, while the rest of the bits may be conveyed inMsg3.

FIG. 9 is a flow chart that illustrates the random access procedure ofEmbodiment 2 from the BS perspective. As illustrated, the BS broadcastsSI including a random access configuration (step 900). The BS receivesMsg1 from the UE (step 902). As discussed above, the UE performsopen-loop timing estimation and uses the resulting open-loop timingestimate to transmit Msg1. Further, Msg1 provides an indication of theopen-loop timing estimate (e.g., the transmitted preamble is from asubgroup of preambles for a defined range of open-loop timingestimates). The BS detects Msg1 and transmits Msg2, where Msg2 includesa closed-loop timing adjustment command (step 904). The BS then receivesMsg3 from the UE (step 906). In scenarios where contention resolution isperformed, the BS transmits Msg4 (step 908).

Embodiment 3

A UE is not required to perform an open-loop TA estimate. Though thePRACH preambles have not been designed to handle long propagation delaysand large differential delays, the BS can use implementation-basedsolutions to estimate the long propagation delays and/or largedifferential delays. In this case, the random access procedure can bekept close to the existing ones, except in Msg2 the BS sends back alarge TA command.

FIG. 10 illustrates a flow chart of a random access procedure from theUE perspective. As illustrated, the UE reads a random accessconfiguration from SI (step 1000). The UE transmits a random accesspreamble (i.e., Msg1) in accordance with the random access configuration(step 1002). The UE subsequently receives a RAR (i.e., Msg2) from theradio access network and further adjusts its TA based on the closed-looptiming adjustment command received in Msg2 (step 1004). In thisembodiment, the TA command is indicative of a large TA value (i.e., a TAvalue that is larger than previously allowed in the TA command, in orderto accommodate the long propagation delays and large differential delaysin a satellite-based radio access network). The UE then transmits Msg3(step 1006). In scenarios where contention resolution is performed, theUE receives Msg4 (step 1008). FIG. 11 further illustrates how the UEadjusts its uplink timing based on the command from the BS.

Next, a few non-limiting examples are given to describe how the stepscould be implemented:

-   -   A separate PRACH resource (in time, frequency, space, and/or        code) may be configured for the UE to transmit Msg1 in this        random access process.    -   A new range for TA command in Msg2 may be defined.        -   Example 1: Extend the TA range [0, Tmax] such that Tmax can            cover the largest TA value envisioned in the deployment. The            number of bits for the TA command and the mapping of a bit            string to a TA value are defined accordingly. For example,            Tmax may be a value greater than 2 ms, a value greater than            10 ms, a value greater than 50 ms, or a value greater than            100 ms, depending on the particular implementation.        -   Example 2: The BS configures T_(min) and T_(max) depending            on the deployment (LEO, MEO, or GEO) and/or cell size and/or            beam size. The number of bits for the TA command and the            mapping of a bit string to a TA value are defined            accordingly.        -   Example 3: The BS configures T_(min) or T_(min) is fixed to            be zero. TA resolution Δ can be the same as the existing            supported value or a newly fixed one or a configurable one.            The number of TA bits is denoted as M, which can be fixed or            configurable. Then the TA range supported is T_(min),            T_(min)+Δ, . . . , T_(min)+(2^(M)−1)*Δ.    -   UE TA procedure        -   The large TA carried in Msg2 may be used in the following            ways:            -   Example 1: The UE applies TA according to the command in                Msg2.            -   Example 2: The UE combines TA in Msg2 and the reference                timing broadcast in SI to form an aggregate TA, and                performs TA using the aggregate TA value.        -   The selection of Examples 1 and 2 above may be configured by            the BS

FIG. 12 is a flow chart that illustrates the random access procedure ofEmbodiment 3 from the BS perspective. As illustrated, the BS broadcastsSI including a random access configuration (step 1200). The BS receivesMsg1 from the UE (step 1202). The BS detects Msg1 and transmits Msg2,where Msg2 includes a timing adjustment command including an extended TAvalue, as discussed above (step 1204). The BS then receives Msg3 fromthe UE (step 1206). In scenarios where contention resolution isperformed, the BS transmits Msg4 (step 1208).

Embodiment 3a

In an alternative option, the BS may broadcast a reference round-tripdelay to UEs based on the largest (or smallest) round-trip signal delay,TA_ref, in the service area. A UE applies a TA equal to TA_ref insending the PRACH in a PRACH resource to the BS. As illustrated in FIG.13, the procedure could include the following steps:

-   -   Step 1300: The BS broadcasts a reference TA, TA_ref, based on        the largest (or the smallest) possible round-trip signal delay        in the service area.    -   Step 1302: The BS allocates PRACH resources in a subframe (or        multiple subframes) periodically.    -   Step 1304: A UE transmits Msg1 aiming for a PRACH opportunity in        an uplink subframe by applying a TA equal to the broadcast        reference time delay, TA_ref.    -   Step 1306: The BS detects PRACH in a time window that covers the        smallest and the largest possible round-trip signal delays. This        may mean a time window over multiple subframes, where the last        (or the first) subframe is the subframe all UEs are aiming for        in case of single subframe PRACH resource configuration.    -   Step 1308: After a PRACH is detected, the BS estimates the TA        for the received Msg1 using the start of the last (or the first)        subframe in the detection window as timing reference.    -   Step 1310: The BS sends a TA in Msg2 consisting of two parts,        i.e. (a) a number of slots, and (b) a fraction of a slot. For a        UE whose actual round-trip delay is the same as or very close to        the broadcast reference round-trip delay, the value of part (a)        should be zero, i.e. the TA is only a fraction of a slot. In        Msg2, a PRACH Identifier (ID) is also included to indicate the        PRACH preamble and the subframe over which the PRACH is        received. A PRACH of a UE aiming for a subframe may actually be        received in a different subframe due to the difference between        the actual round-trip delay and the broadcast reference round        trip delay. One solution may be to use the last subframe (or the        first) in the detection window as the receive subframe when        forming the PRACH ID, i.e. using the subframe configured for        PRACH in the detection window to form the PRACH ID.    -   Step 1312: After receiving Msg2 and the PRACH ID matches the        UE's transmitted PRACH, a UE sends Msg3 by applying an        additional TA correction received in Msg2 and a subframe offset        either predetermined or signaled in Msg2.

By broadcasting a reference round-trip delay to UEs based on the largest(or smallest) round-trip signal delay, TA_ref, in the service area and aUE applies a TA equal to TA_ref, the BS would know the actual round-tripdelay of the UE after receiving Msg1. It is possible to align uplinksignals such as Physical Uplink Shared Channel (PUSCH), Physical UplinkControl Channel (PUCCH) from UEs with different round-trip delays in thesame uplink subframe.

Embodiment 4

The UE is not required to perform open-loop TA estimate. Though thePRACH preambles have not been designed to handle long propagation delayand large differential delay, the BS can use implementation-basedsolutions to estimate the long propagation delay and/or largedifferential delay. In this case, the random access procedure can bekept close to the existing ones and in Msg2 the BS sends back a TAcommand only to align subframe boundary.

FIG. 14 illustrates a flow chart of the random access procedure from theUE perspective. As illustrated, the UE reads a random accessconfiguration from SI (step 1400). The UE transmits a random accesspreamble (i.e., Msg1) in accordance with the random access configuration(step 1402). The UE subsequently receives a random access response(i.e., Msg2) from the radio access network and further adjusts its TAbased on the closed-loop timing adjustment command received in Msg2(step 1404). In this embodiment, the TA command includes a TA command toalign the subframe boundary. The UE then transmits Msg3 (step 1406). Inscenarios where contention resolution is performed, the UE receives Msg4(step 1408). FIG. 15 further illustrates how the UE adjusts its uplinktiming based on the command from the BS.

Next, a few non-limiting examples are given to describe how the stepsmay be implemented:

-   -   TA for subframe alignment        -   Example 1: timing adjust with bipolar TA values with range            [−0.5 ms, 0.5 ms]            -   The BS can command the UE to advance (with a positive TA                value) or delay (with a negative TA value) uplink timing                to align to the subframe boundary.        -   Example 2: timing adjust with unipolar TA values with range            [0 ms, 1 ms]            -   The BS can command the UE to advance uplink timing to                align to the subframe boundary.    -   Estimation and communication of propagation delay (some        procedures below do not have to be part of the random access        procedure)        -   Though not required, the UE may perform an estimate of            propagation delay and/or differential delay.            -   The UE may indicate to the BS about its capability of                such estimates.            -   The UE may be triggered to perform these estimates.            -   The BS may poll the UE to report the estimates from the                UE to the BS.        -   Alternatively, the BS can use implementation-based solutions            to estimate the propagation delay and/or differential delay.            -   The BS may provide the UE with the estimates to assist                with UE behaviors.

FIG. 16 is a flow chart that illustrates the random access procedure ofEmbodiment 4 from the BS perspective. As illustrated, the BS broadcastsSI including a random access configuration (step 1600). The BS receivesMsg1 from the UE (step 1602). The BS detects Msg1 and transmits Msg2,where Msg2 includes a timing adjustment command including a TA value forsubframe boundary alignment, as discussed above (step 1604). The BS thenreceives Msg3 from the UE (step 1606). In scenarios where contentionresolution is performed, the BS transmits Msg4 (step 1608).

Embodiment 5

The UE is not required to do open-loop timing estimates nor is the BSrequired to do its own estimation. The procedure is designed in order toprovide both the UE and BS (e.g., eNB) necessary information toaccurately estimate the propagation delay. By dividing the PRACHpreambles into different subframes, the network will ensure that two UEswith different delays will not collide with the same preambles.

Next, a set of non-limiting examples are provided below. This process isillustrated in FIG. 17:

-   -   The PRACH preambles are divided in to N groups pg_1, pg_2, . . .        , pg_N−1 where each group is assigned one subframe. This        subframe pattern is then repeated every M subframes in which        M≥N.        -   N as an example should be the maximum differential delay.        -   M as an example can also be set to the maximum differential            delay.    -   Step 1700: The BS provides the following configurations in SI:        -   N,        -   M, and        -   minimum propagation delay of the spotbeam/cell as the            reference timing value.    -   Steps 1702 and 1704: The UE selects RA-RNTI and preamble, and        transmits Msg1 in the corresponding subframe.        -   The RA-RNTI is calculated as RA-RNTI=1+pg_id+M*f_id, where            -   pg_id is the preamble group between 0 and M−1, and            -   f_id is between 0 and 5.    -   Step 1706: The reception of Msg1 from the UE allows the BS to        estimate the propagation delay.    -   Step 1708: The BS transmits Msg2 with the UEs selected RA-RNTI,        and the UE waits for the Msg2 with its selected RA-RNTI, which        contains the following:        -   an extended TA=[−0.5, 0.5] ms, and        -   the BS delay between reception of Msg1 and transmission of            Msg2.            -   This delay can for example be signaled as a four bit                field, which would make the maximum delay 16 ms.    -   Step 1710: The reception of Msg2 allows the UE to accurately        estimate its propagation delay using the measured time between        transmission of Msg1, reception of Msg2, and TA delay and BS        delay in Msg2.    -   Step 1712: The UE sends Msg3 applying the TA        -   The UE may optionally include propagation delay in Msg3.            This can be used for contention resolution if the BS            receives two Msg3 with the same RA-RNTI but with different            signaled propagation delays.

Additional Aspects

FIG. 18 is a schematic block diagram of a radio access node 1800 (e.g.,a BS) according to some embodiments of the present disclosure. The radioaccess node 1800 may be, for example, a satellite based radio accessnode. As illustrated, the radio access node 1800 includes a controlsystem 1802 that includes one or more processors 1804 (e.g., CentralProcessing Units (CPUs), Application Specific Integrated Circuits(ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like),memory 1806, and a network interface 1808. The one or more processors1804 are also referred to herein as processing circuitry. In addition,the radio access node 1800 includes one or more radio units 1810 thateach includes one or more transmitters 1812 and one or more receivers1814 coupled to one or more antennas 1816. The radio units 1810 may bereferred to or be part of radio interface circuitry. In someembodiments, the radio unit(s) 1810 is external to the control system1802 and connected to the control system 1802 via, e.g., a wiredconnection (e.g., an optical cable). However, in some other embodiments,the radio unit(s) 1810 and potentially the antenna(s) 1816 areintegrated together with the control system 1802. The one or moreprocessors 1804 operate to provide one or more functions of a radioaccess node 1800 as described herein. In some embodiments, thefunction(s) are implemented in software that is stored, e.g., in thememory 1806 and executed by the one or more processors 1804.

In some embodiments, both the control system 1802 and the radio unit(s)1810 are implemented in the satellite, e.g., of FIG. 1. As one examplealternative, the radio unit(s) may be implemented in the satellite,e.g., of FIG. 1 and the control system 1802 may be implemented in aland-based component of the radio access node that is communicativelycoupled to the satellite via the gateway, e.g., of FIG. 1.

FIG. 19 is a schematic block diagram that illustrates a virtualizedembodiment of the radio access node 1800 according to some embodimentsof the present disclosure. This discussion is equally applicable toother types of network nodes. Further, other types of network nodes mayhave similar virtualized architectures.

As used herein, a “virtualized” radio access node is an implementationof the radio access node 1800 in which at least a portion of thefunctionality of the radio access node 1800 is implemented as a virtualcomponent(s) (e.g., via a virtual machine(s) executing on a physicalprocessing node(s) in a network(s)). As illustrated, in this example,the radio access node 1800 includes the control system 1802 thatincludes the one or more processors 1804 (e.g., CPUs, ASICs, FPGAs,and/or the like), the memory 1806, and the network interface 1808 andthe one or more radio units 1810 that each includes the one or moretransmitters 1812 and the one or more receivers 1814 coupled to the oneor more antennas 1816, as described above. The control system 1802 isconnected to the radio unit(s) 1810 via, for example, an optical cableor the like. The control system 1802 is connected to one or moreprocessing nodes 1900 coupled to or included as part of a network(s)1902 via the network interface 1808. Each processing node 1900 includesone or more processors 1904 (e.g., CPUs, ASICs, FPGAs, and/or the like),memory 1906, and a network interface 1908.

In this example, functions 1910 of the radio access node 1800 describedherein are implemented at the one or more processing nodes 1900 ordistributed across the control system 1802 and the one or moreprocessing nodes 1900 in any desired manner. In some particularembodiments, some or all of the functions 1910 of the radio access node1800 described herein are implemented as virtual components executed byone or more virtual machines implemented in a virtual environment(s)hosted by the processing node(s) 1900. As will be appreciated by one ofordinary skill in the art, additional signaling or communication betweenthe processing node(s) 1900 and the control system 1802 is used in orderto carry out at least some of the desired functions 1910. Notably, insome embodiments, the control system 1802 may not be included, in whichcase the radio unit(s) 1810 communicate directly with the processingnode(s) 1900 via an appropriate network interface(s).

In some embodiments, a computer program including instructions which,when executed by at least one processor, causes the at least oneprocessor to carry out the functionality of radio access node 1800 or anode (e.g., a processing node 1900) implementing one or more of thefunctions 1910 of the radio access node 1800 in a virtual environmentaccording to any of the embodiments described herein is provided. Insome embodiments, a carrier comprising the aforementioned computerprogram product is provided. The carrier is one of an electronic signal,an optical signal, a radio signal, or a computer readable storage medium(e.g., a non-transitory computer readable medium such as memory).

FIG. 20 is a schematic block diagram of the radio access node 1800according to some other embodiments of the present disclosure. The radioaccess node 1800 includes one or more modules 2000, each of which isimplemented in software. The module(s) 2000 provide the functionality ofthe radio access node 1800 described herein. This discussion is equallyapplicable to the processing node 1900 of FIG. 19 where the modules 2000may be implemented at one of the processing nodes 1900 or distributedacross multiple processing nodes 1900 and/or distributed across theprocessing node(s) 1900 and the control system 1802.

FIG. 21 is a schematic block diagram of a UE 2100 according to someembodiments of the present disclosure. As illustrated, the UE 2100includes one or more processors 2102 (e.g., CPUs, ASICs, FPGAs, and/orthe like), memory 2104, and one or more transceivers 2106 each includingone or more transmitters 2108 and one or more receivers 2110 coupled toone or more antennas 2112. The transceiver(s) 2106 includes radio-frontend circuitry connected to the antenna(s) 2112 that is configured tocondition signals communicated between the antenna(s) 2112 and theprocessor(s) 2102, as will be appreciated by on of ordinary skill in theart. The processors 2102 are also referred to herein as processingcircuitry. The transceivers 2106 are also referred to herein as radiocircuitry. In some embodiments, the functionality of the UE 2100described above may be fully or partially implemented in software thatis, e.g., stored in the memory 2104 and executed by the processor(s)2102. Note that the UE 2100 may include additional components notillustrated in FIG. 21 such as, e.g., one or more user interfacecomponents (e.g., an input/output interface including a display,buttons, a touch screen, a microphone, a speaker(s), and/or the likeand/or any other components for allowing input of information into theUE 2100 and/or allowing output of information from the UE 2100), a powersupply (e.g., a battery and associated power circuitry), etc.

In some embodiments, a computer program including instructions which,when executed by at least one processor, causes the at least oneprocessor to carry out the functionality of the UE 2100 according to anyof the embodiments described herein is provided. In some embodiments, acarrier comprising the aforementioned computer program product isprovided. The carrier is one of an electronic signal, an optical signal,a radio signal, or a computer readable storage medium (e.g., anon-transitory computer readable medium such as memory).

FIG. 22 is a schematic block diagram of the UE 2100 according to someother embodiments of the present disclosure. The UE 2100 includes one ormore modules 2200, each of which is implemented in software. Themodule(s) 2200 provide the functionality of the UE 1500 describedherein.

With reference to FIG. 23, in accordance with an embodiment, acommunication system includes a telecommunication network 2300, such asa 3GPP-type cellular network, which comprises an access network 2302,such as a Radio Access Network (RAN), and a core network 2304. Theaccess network 2302 comprises a plurality of base stations 2306A, 2306B,2306C, such as Node Bs, eNBs, gNBs, or other types of wireless AccessPoints (APs), each defining a corresponding coverage area 2308A, 2308B,2308C. Note that some or all of the APs, in some embodiments,satellite-based base stations as described herein. Each base station2306A, 2306B, 2306C is connectable to the core network 2304 over a wiredor wireless connection 2310. A first UE 2312 located in coverage area2308C is configured to wirelessly connect to, or be paged by, thecorresponding base station 2306C. A second UE 2314 in coverage area2308A is wirelessly connectable to the corresponding base station 2306A.While a plurality of UEs 2312, 2314 are illustrated in this example, thedisclosed embodiments are equally applicable to a situation where a soleUE is in the coverage area or where a sole UE is connecting to thecorresponding base station 2306.

The telecommunication network 2300 is itself connected to a hostcomputer 2316, which may be embodied in the hardware and/or software ofa standalone server, a cloud-implemented server, a distributed server,or as processing resources in a server farm. The host computer 2316 maybe under the ownership or control of a service provider, or may beoperated by the service provider or on behalf of the service provider.Connections 2318 and 2320 between the telecommunication network 2300 andthe host computer 2316 may extend directly from the core network 2304 tothe host computer 2316 or may go via an optional intermediate network2322. The intermediate network 2322 may be one of, or a combination ofmore than one of, a public, private, or hosted network; the intermediatenetwork 2322, if any, may be a backbone network or the Internet; inparticular, the intermediate network 2322 may comprise two or moresub-networks (not shown).

The communication system of FIG. 23 as a whole enables connectivitybetween the connected UEs 2312, 2314 and the host computer 2316. Theconnectivity may be described as an Over-the-Top (OTT) connection 2324.The host computer 2316 and the connected UEs 2312, 2314 are configuredto communicate data and/or signaling via the OTT connection 2324, usingthe access network 2302, the core network 2304, any intermediate network2322, and possible further infrastructure (not shown) as intermediaries.The OTT connection 2324 may be transparent in the sense that theparticipating communication devices through which the OTT connection2324 passes are unaware of routing of uplink and downlinkcommunications. For example, the base station 2306 may not or need notbe informed about the past routing of an incoming downlink communicationwith data originating from the host computer 2316 to be forwarded (e.g.,handed over) to a connected UE 2312. Similarly, the base station 2306need not be aware of the future routing of an outgoing uplinkcommunication originating from the UE 2312 towards the host computer2316.

Example implementations, in accordance with an embodiment, of the UE,base station, and host computer discussed in the preceding paragraphswill now be described with reference to FIG. 24. In a communicationsystem 2400, a host computer 2402 comprises hardware 2404 including acommunication interface 2406 configured to set up and maintain a wiredor wireless connection with an interface of a different communicationdevice of the communication system 2400. The host computer 2402 furthercomprises processing circuitry 2408, which may have storage and/orprocessing capabilities. In particular, the processing circuitry 2408may comprise one or more programmable processors, ASICs, FPGAs, orcombinations of these (not shown) adapted to execute instructions. Thehost computer 2402 further comprises software 2410, which is stored inor accessible by the host computer 2402 and executable by the processingcircuitry 2408. The software 2410 includes a host application 2412. Thehost application 2412 may be operable to provide a service to a remoteuser, such as a UE 2414 connecting via an OTT connection 2416terminating at the UE 2414 and the host computer 2402. In providing theservice to the remote user, the host application 2412 may provide userdata which is transmitted using the OTT connection 2416.

The communication system 2400 further includes a base station 2418provided in a telecommunication system and comprising hardware 2420enabling it to communicate with the host computer 2402 and with the UE2414. The hardware 2420 may include a communication interface 2422 forsetting up and maintaining a wired or wireless connection with aninterface of a different communication device of the communicationsystem 2400, as well as a radio interface 2424 for setting up andmaintaining at least a wireless connection 2426 with the UE 2414 locatedin a coverage area (not shown in FIG. 24) served by the base station2418. The communication interface 2422 may be configured to facilitate aconnection 2428 to the host computer 2402. The connection 2428 may bedirect or it may pass through a core network (not shown in FIG. 24) ofthe telecommunication system and/or through one or more intermediatenetworks outside the telecommunication system. In the embodiment shown,the hardware 2420 of the base station 2418 further includes processingcircuitry 2430, which may comprise one or more programmable processors,ASICs, FPGAs, or combinations of these (not shown) adapted to executeinstructions. The base station 2418 further has software 2432 storedinternally or accessible via an external connection.

The communication system 2400 further includes the UE 2414 alreadyreferred to. The UE's 2414 hardware 2434 may include a radio interface2436 configured to set up and maintain a wireless connection 2426 with abase station serving a coverage area in which the UE 2414 is currentlylocated. The hardware 2434 of the UE 2414 further includes processingcircuitry 2438, which may comprise one or more programmable processors,ASICs, FPGAs, or combinations of these (not shown) adapted to executeinstructions. The UE 2414 further comprises software 2440, which isstored in or accessible by the UE 2414 and executable by the processingcircuitry 2438. The software 2440 includes a client application 2442.The client application 2442 may be operable to provide a service to ahuman or non-human user via the UE 2414, with the support of the hostcomputer 2402. In the host computer 2402, the executing host application2412 may communicate with the executing client application 2442 via theOTT connection 2416 terminating at the UE 2414 and the host computer2402. In providing the service to the user, the client application 2442may receive request data from the host application 2412 and provide userdata in response to the request data. The OTT connection 2416 maytransfer both the request data and the user data. The client application2442 may interact with the user to generate the user data that itprovides.

It is noted that the host computer 2402, the base station 2418, and theUE 2414 illustrated in FIG. 24 may be similar or identical to the hostcomputer 2316, one of the base stations 2306A, 2306B, 2306C, and one ofthe UEs 2312, 2314 of FIG. 23, respectively. This is to say, the innerworkings of these entities may be as shown in FIG. 24 and independently,the surrounding network topology may be that of FIG. 23.

In FIG. 24, the OTT connection 2416 has been drawn abstractly toillustrate the communication between the host computer 2402 and the UE2414 via the base station 2418 without explicit reference to anyintermediary devices and the precise routing of messages via thesedevices. The network infrastructure may determine the routing, which maybe configured to hide from the UE 2414 or from the service provideroperating the host computer 2402, or both. While the OTT connection 2416is active, the network infrastructure may further take decisions bywhich it dynamically changes the routing (e.g., on the basis of loadbalancing consideration or reconfiguration of the network).

The wireless connection 2426 between the UE 2414 and the base station2418 is in accordance with the teachings of the embodiments describedthroughout this disclosure. One or more of the various embodimentsimprove the performance of OTT services provided to the UE 2414 usingthe OTT connection 2416, in which the wireless connection 2426 forms thelast segment. More precisely, the teachings of these embodiments mayimprove, e.g., data rate, latency, and/or power consumption and therebyprovide benefits such as, e.g., reduced user waiting time, relaxedrestriction on file size, better responsiveness, and/or extended batterylifetime.

A measurement procedure may be provided for the purpose of monitoringdata rate, latency, and other factors on which the one or moreembodiments improve. There may further be an optional networkfunctionality for reconfiguring the OTT connection 2416 between the hostcomputer 2402 and the UE 2414, in response to variations in themeasurement results. The measurement procedure and/or the networkfunctionality for reconfiguring the OTT connection 2416 may beimplemented in the software 2410 and the hardware 2404 of the hostcomputer 2402 or in the software 2440 and the hardware 2434 of the UE2414, or both. In some embodiments, sensors (not shown) may be deployedin or in association with communication devices through which the OTTconnection 2416 passes; the sensors may participate in the measurementprocedure by supplying values of the monitored quantities exemplifiedabove, or supplying values of other physical quantities from which thesoftware 2410, 2440 may compute or estimate the monitored quantities.The reconfiguring of the OTT connection 2416 may include message format,retransmission settings, preferred routing, etc.; the reconfiguring neednot affect the base station 2418, and it may be unknown or imperceptibleto the base station 2418. Such procedures and functionalities may beknown and practiced in the art. In certain embodiments, measurements mayinvolve proprietary UE signaling facilitating the host computer 2402'smeasurements of throughput, propagation times, latency, and the like.The measurements may be implemented in that the software 2410 and 2440causes messages to be transmitted, in particular empty or ‘dummy’messages, using the OTT connection 2416 while it monitors propagationtimes, errors, etc.

FIG. 25 is a flowchart illustrating a method implemented in acommunication system, in accordance with one embodiment. Thecommunication system includes a host computer, a base station, and a UEwhich may be those described with reference to FIGS. 23 and 24. Forsimplicity of the present disclosure, only drawing references to FIG. 25will be included in this section. In step 2500, the host computerprovides user data. In sub-step 2502 (which may be optional) of step2500, the host computer provides the user data by executing a hostapplication. In step 2504, the host computer initiates a transmissioncarrying the user data to the UE. In step 2506 (which may be optional),the base station transmits to the UE the user data which was carried inthe transmission that the host computer initiated, in accordance withthe teachings of the embodiments described throughout this disclosure.In step 2508 (which may also be optional), the UE executes a clientapplication associated with the host application executed by the hostcomputer.

FIG. 26 is a flowchart illustrating a method implemented in acommunication system, in accordance with one embodiment. Thecommunication system includes a host computer, a base station, and a UEwhich may be those described with reference to FIGS. 23 and 24. Forsimplicity of the present disclosure, only drawing references to FIG. 26will be included in this section. In step 2600 of the method, the hostcomputer provides user data. In an optional sub-step (not shown) thehost computer provides the user data by executing a host application. Instep 2602, the host computer initiates a transmission carrying the userdata to the UE. The transmission may pass via the base station, inaccordance with the teachings of the embodiments described throughoutthis disclosure. In step 2604 (which may be optional), the UE receivesthe user data carried in the transmission.

FIG. 27 is a flowchart illustrating a method implemented in acommunication system, in accordance with one embodiment. Thecommunication system includes a host computer, a base station, and a UEwhich may be those described with reference to FIGS. 23 and 24. Forsimplicity of the present disclosure, only drawing references to FIG. 27will be included in this section. In step 2700 (which may be optional),the UE receives input data provided by the host computer. Additionallyor alternatively, in step 2702, the UE provides user data. In sub-step2704 (which may be optional) of step 2700, the UE provides the user databy executing a client application. In sub-step 2706 (which may beoptional) of step 2702, the UE executes a client application whichprovides the user data in reaction to the received input data providedby the host computer. In providing the user data, the executed clientapplication may further consider user input received from the user.Regardless of the specific manner in which the user data was provided,the UE initiates, in sub-step 2708 (which may be optional), transmissionof the user data to the host computer. In step 2710 of the method, thehost computer receives the user data transmitted from the UE, inaccordance with the teachings of the embodiments described throughoutthis disclosure.

FIG. 28 is a flowchart illustrating a method implemented in acommunication system, in accordance with one embodiment. Thecommunication system includes a host computer, a base station, and a UEwhich may be those described with reference to FIGS. 23 and 24. Forsimplicity of the present disclosure, only drawing references to FIG. 28will be included in this section. In step 2800 (which may be optional),in accordance with the teachings of the embodiments described throughoutthis disclosure, the base station receives user data from the UE. Instep 2802 (which may be optional), the base station initiatestransmission of the received user data to the host computer. In step2804 (which may be optional), the host computer receives the user datacarried in the transmission initiated by the base station.

While processes in the figures may show a particular order of operationsperformed by certain embodiments of the present disclosure, it should beunderstood that such order is exemplary (e.g., alternative embodimentsmay perform the operations in a different order, combine certainoperations, overlap certain operations, etc.).

Some example embodiments of the present disclosure are as follows.

Embodiment 1: A method performed by a wireless device for random access,the method comprising: performing an open-loop timing advance estimationprocedure to thereby determine an open-loop timing advance estimate foran uplink between the wireless device and a base station; transmitting arandom access preamble using the open-loop timing advance estimate.

Embodiment 2: The method of embodiment 1 further comprising: receiving,from the base station, a random access response comprising a timingadvance value; and determining a timing advance for the uplink betweenthe wireless device and the base station based on the timing advancevalue comprised in the random access response and the open-loop timingadvance estimate.

Embodiment 3: The method of embodiment 2 wherein the random accessresponse schedules resources for an uplink transmission from thewireless device, and the method further comprises: transmitting anuplink transmission to the base station using the scheduled resourcesand the determined timing advance, the uplink transmission comprising anidentity of the wireless device and an indication of the open-looptiming advance estimate.

Embodiment 4: The method of embodiment 3 wherein the indication of theopen-loop timing advance estimate is the open-loop timing advanceestimate.

Embodiment 5: The method of embodiment 3 wherein the indication of theopen-loop timing advance estimate is a differential value that equals adifference between the open-loop timing advance estimate and apredefined or preconfigured reference value.

Embodiment 6: The method of embodiment 1 wherein the random accesspreamble is a function of the open-loop timing estimate.

Embodiment 7: The method of embodiment 1 further comprising selectingthe random access preamble from a subgroup of a plurality of possiblyrandom access preambles, the subgroup being chosen based on theopen-loop timing estimate.

Embodiment 8: The method of embodiment 6 or 7 wherein the random accesspreamble provides an indication of the open-loop timing advanceestimate.

Embodiment 9: The method of any one of embodiments 6 to 7 furthercomprising: receiving, from the base station, a random access responsecomprising a timing advance value; and determining a timing advance forthe uplink between the wireless device and the base station based on thetiming advance value comprised in the random access response and theopen-loop timing advance estimate.

Embodiment 10: The method of embodiment 9 wherein the random accessresponse schedules resources for an uplink transmission from thewireless device, and the method further comprises: transmitting anuplink transmission to the base station using the scheduled resourcesand the determined timing advance, the uplink transmission comprising anidentity of the wireless device and information that, together with therandom access preamble transmitted by the wireless device, provide anindication of the open-loop timing advance estimate.

Embodiment 11: The method of any one of embodiments 1 to 10 wherein thebase station is part of a satellite radio access network comprising asatellite and a gateway that communicatively couples the base station tothe satellite.

Embodiment 12: A method performed by a wireless device for random accessin a radio access network, the method comprising: transmitting a randomaccess preamble; and receiving, from a base station, a random accessresponse comprising a timing advance value, the timing advance valuebeing greater than 2 ms.

Embodiment 13: The method of embodiment 12 wherein the timing advancevalue is greater than 10 ms.

Embodiment 14: The method of embodiment 12 wherein the timing advancevalue is greater than 50 ms.

Embodiment 15: The method of embodiment 12 wherein the timing advancevalue is greater than 100 ms.

Embodiment 16: The method of any one of embodiments 12 to 15 wherein thetiming advance value is within a range of T_(min) to T_(max), whereinT_(min) and/or T_(max) are a function of a deployment of the radioaccess network.

Embodiment 17: The method of any one of embodiments 12 to 16 wherein thebase station is part of a satellite radio access network comprising asatellite and a gateway that communicatively couples the base station tothe satellite.

Embodiment 18: The method of embodiment 17 wherein the timing advancevalue is within a range of T_(min) to T_(max), wherein T_(min) and/orT_(max) are a function of whether the satellite is a LEO, MEO, or GEO.

Embodiment 19: A method performed by a wireless device for random accessin a radio access network, the method comprising: receiving, from a basestation, a reference timing advance; transmitting a random accesspreamble using a timing advance that is equal to the reference timingadvance.

Embodiment 20: The method of embodiment 19 further comprising receiving,from a base station, a random access response comprising informationthat, together with the reference timing advance, indicates a timingadvance value for the wireless device.

Embodiment 21: The method of embodiment 20 wherein the informationcomprises a number of slots and a fraction of a slot.

Embodiment 22: The method of any one of embodiments 19 to 21 wherein thebase station is part of a satellite radio access network comprising asatellite and a gateway that communicatively couples the base station tothe satellite.

Embodiment 23: A method performed by a wireless device for random accessin a radio access network, the method comprising: transmitting a randomaccess preamble; and receiving, from a base station, a random accessresponse comprising a timing advance value for subframe boundaryalignment.

Embodiment 24: The method of embodiment 23 further comprisingtransmitting, to the base station, an indication that the wirelessdevice is capable of performing open-loop timing advance estimation.

Embodiment 25: The method of embodiment 24 wherein the indication istransmitted during random access or outside of random access.

Embodiment 26: The method of any one of embodiments 23 to 25 wherein thebase station is part of a satellite radio access network comprising asatellite and a gateway that communicatively couples the base station tothe satellite.

Embodiment 27: A method performed by a wireless device for random accessin a radio access network, the method comprising: transmitting anindication to a base station that the wireless device is capable ofperforming open-loop timing advance estimation.

Embodiment 28: The method of embodiment 27 wherein the base station ispart of a satellite radio access network comprising a satellite and agateway that communicatively couples the base station to the satellite.

Embodiment 29: A method performed by a wireless device for random accessin a radio access network, the method comprising: transmitting a randomaccess preamble; and receiving, from a base station, a random accessresponse comprising information that indicates a processing latency atthe base station between reception of the random access preamble by thebase station and transmission of the random access response by the basestation; estimating a round-trip propagation delay of the wirelessdevice by subtracting the processing latency at the base station from atime duration between transmission of the random access preamble at thewireless device and receiving the random access response at the wirelessdevice.

Embodiment 30: The method of embodiment 29 wherein the base station ispart of a satellite radio access network comprising a satellite and agateway that communicatively couples the base station to the satellite.

Embodiment 31: The method of any of the previous embodiments, furthercomprising: providing user data; and forwarding the user data to a hostcomputer via the transmission to the base station.

Embodiment 32: A method performed by a base station for enabling randomaccess in a radio access network, the method comprising: detecting arandom access preamble from a wireless device; transmitting a randomaccess response comprising a timing advance value; and receiving, fromthe wireless device, an uplink transmission, the uplink transmissioncomprising an identity of the wireless device and an indication of theopen-loop timing advance estimate.

Embodiment 33: The method of embodiment 32 wherein the base station ispart of a satellite radio access network comprising a satellite and agateway that communicatively couples the base station to the satellite.

Embodiment 34: A method performed by a base station for enabling randomaccess in a radio access network, the method comprising: detecting arandom access preamble from a wireless device, the random accesspreamble being a function of an open-loop timing advance estimate of thewireless device; and transmitting, to the wireless device, a randomaccess response comprising a timing advance value.

Embodiment 35: The method of embodiment 34 wherein the random accesspreamble is from a subgroup of a plurality of possibly random accesspreambles, the subgroup being indicative of the open-loop timingestimate.

Embodiment 36: The method of embodiment 34 or 35 wherein the randomaccess preamble provides an indication of the open-loop timing advanceestimate.

Embodiment 37: The method of embodiment 34 or 35 further comprising:receiving, from wireless device, an uplink transmission comprising anidentity of the wireless device and information that, together with therandom access preamble transmitted by the wireless device, provide anindication of the open-loop timing advance estimate.

Embodiment 38: The method of any embodiments 34 to 37 wherein the basestation is part of a satellite radio access network comprising asatellite and a gateway that communicatively couples the base station tothe satellite.

Embodiment 39: A method performed by a base station for enabling randomaccess in a radio access network, the method comprising: detecting arandom access preamble from a wireless device; and transmitting, to thewireless device, a random access response comprising a timing advancevalue, the timing advance value being greater than 2 ms.

Embodiment 40: The method of embodiment 39 wherein the timing advancevalue is greater than 10 ms.

Embodiment 41: The method of embodiment 39 wherein the timing advancevalue is greater than 50 ms.

Embodiment 42: The method of embodiment 39 wherein the timing advancevalue is greater than 100 ms.

Embodiment 43: The method of any one of embodiments 39 to 42 wherein thetiming advance value is within a range of T_(min) to T_(max), whereinT_(min) and/or T_(max) are a function of a deployment of the radioaccess network.

Embodiment 44: The method of any one of embodiments 39 to 43 wherein thebase station is part of a satellite radio access network comprising asatellite and a gateway that communicatively couples the base station tothe satellite.

Embodiment 45: The method of embodiment 44 wherein the timing advancevalue is within a range of T_(min) to T_(max), wherein T_(min) and/orT_(max) are a function of whether the satellite is a LEO, MEO, or GEO.

Embodiment 46: A method performed by a base station for enabling randomaccess in a radio access network, the method comprising: transmitting,to one or more wireless devices, a reference timing advance; detecting arandom access preamble from a wireless device; and transmitting, to thewireless device, a random access response comprising information that,together with the reference timing advance, indicates a timing advancevalue for the wireless device.

Embodiment 47: The method of embodiment 46 wherein the informationcomprises a number of slots and a fraction of a slot.

Embodiment 48: The method of embodiment 46 or 47 wherein the basestation is part of a satellite radio access network comprising asatellite and a gateway that communicatively couples the base station tothe satellite.

Embodiment 49: A method performed by a base station for enabling randomaccess in a radio access network, the method comprising: detecting arandom access preamble from a wireless device; and transmitting, to thewireless device, a random access response comprising a timing advancevalue for subframe boundary alignment.

Embodiment 50: The method of embodiment 49 further comprising receiving,from the wireless device, an indication that the wireless device iscapable of performing open-loop timing advance estimation.

Embodiment 51: The method of embodiment 50 wherein the indication isreceived during random access or outside of random access.

Embodiment 52: The method of any one of embodiments 49 to 51 wherein thebase station is part of a satellite radio access network comprising asatellite and a gateway that communicatively couples the base station tothe satellite.

Embodiment 53: A method performed by a base station for enabling randomaccess in a radio access network, the method comprising: receiving, froma wireless device, an indication that the wireless device is capable ofperforming open-loop timing advance estimation.

Embodiment 54: The method of embodiment 53 wherein the base station ispart of a satellite radio access network comprising a satellite and agateway that communicatively couples the base station to the satellite.

Embodiment 55: A method performed by a base station for enabling randomaccess in a radio access network, the method comprising: detecting arandom access preamble from a wireless device; and transmitting, to thewireless device, a random access response comprising information thatindicates a processing latency at the base station between reception ofthe random access preamble by the base station and transmission of therandom access response by the base station.

Embodiment 56: The method of embodiment 55 wherein the base station ispart of a satellite radio access network comprising a satellite and agateway that communicatively couples the base station to the satellite.

Embodiment 57: The method of any of the previous embodiments, furthercomprising: obtaining user data; and forwarding the user data to a hostcomputer or a wireless device.

Embodiment 58: A wireless device for random access in a radio accessnetwork, the wireless device comprising: processing circuitry configuredto perform any of the steps of any one of embodiments 1 to 31; and powersupply circuitry configured to supply power to the wireless device.

Embodiment 59: A base station for enabling random access in a radioaccess network, the base station comprising: processing circuitryconfigured to perform any of the steps of any one of embodiments 32 to57; and power supply circuitry configured to supply power to the basestation.

Embodiment 60: A User Equipment, UE, for random access in a radio accessnetwork, the UE comprising: an antenna configured to send and receivewireless signals; radio front-end circuitry connected to the antenna andto processing circuitry, and configured to condition signalscommunicated between the antenna and the processing circuitry; theprocessing circuitry being configured to perform any of the steps of anyone of embodiments 1 to 31; an input interface connected to theprocessing circuitry and configured to allow input of information intothe UE to be processed by the processing circuitry; an output interfaceconnected to the processing circuitry and configured to outputinformation from the UE that has been processed by the processingcircuitry; and a battery connected to the processing circuitry andconfigured to supply power to the UE.

Embodiment 61: A communication system including a host computercomprising: processing circuitry configured to provide user data; and acommunication interface configured to forward the user data to acellular network for transmission to a User Equipment, UE; wherein thecellular network comprises a base station having a radio interface andprocessing circuitry, the base station's processing circuitry configuredto perform any of the steps of any one of embodiments 32 to 57.

Embodiment 62: The communication system of the previous embodimentfurther including the base station.

Embodiment 63: The communication system of the previous 2 embodiments,further including the UE, wherein the UE is configured to communicatewith the base station.

Embodiment 64: The communication system of the previous 3 embodiments,wherein: the processing circuitry of the host computer is configured toexecute a host application, thereby providing the user data; and the UEcomprises processing circuitry configured to execute a clientapplication associated with the host application.

Embodiment 65: A method implemented in a communication system includinga host computer, a base station, and a User Equipment, UE, the methodcomprising: at the host computer, providing user data; and at the hostcomputer, initiating a transmission carrying the user data to the UE viaa cellular network comprising the base station, wherein the base stationperforms any of the steps of any one of embodiments 32 to 57.

Embodiment 66: The method of the previous embodiment, furthercomprising, at the base station, transmitting the user data.

Embodiment 67: The method of the previous 2 embodiments, wherein theuser data is provided at the host computer by executing a hostapplication, the method further comprising, at the UE, executing aclient application associated with the host application.

Embodiment 68: A User Equipment, UE, configured to communicate with abase station, the UE comprising a radio interface and processingcircuitry configured to perform the method of the previous 3embodiments.

Embodiment 69: A communication system including a host computercomprising: processing circuitry configured to provide user data; and acommunication interface configured to forward user data to a cellularnetwork for transmission to a User Equipment, UE; wherein the UEcomprises a radio interface and processing circuitry, the UE'scomponents configured to perform any of the steps of any one ofembodiments 1 to 31.

Embodiment 70: The communication system of the previous embodiment,wherein the cellular network further includes a base station configuredto communicate with the UE.

Embodiment 71: The communication system of the previous 2 embodiments,wherein: the processing circuitry of the host computer is configured toexecute a host application, thereby providing the user data; and theUE's processing circuitry is configured to execute a client applicationassociated with the host application.

Embodiment 72: A method implemented in a communication system includinga host computer, a base station, and a User Equipment, UE, the methodcomprising: at the host computer, providing user data; and at the hostcomputer, initiating a transmission carrying the user data to the UE viaa cellular network comprising the base station, wherein the UE performsany of the steps of any one of embodiments 1 to 31.

Embodiment 73: The method of the previous embodiment, further comprisingat the UE, receiving the user data from the base station.

Embodiment 74: A communication system including a host computercomprising: communication interface configured to receive user dataoriginating from a transmission from a User Equipment, UE, to a basestation; wherein the UE comprises a radio interface and processingcircuitry, the UE's processing circuitry configured to perform any ofthe steps of any one of embodiments 1 to 31.

Embodiment 75: The communication system of the previous embodiment,further including the UE.

Embodiment 76: The communication system of the previous 2 embodiments,further including the base station, wherein the base station comprises aradio interface configured to communicate with the UE and acommunication interface configured to forward to the host computer theuser data carried by a transmission from the UE to the base station.

Embodiment 77: The communication system of the previous 3 embodiments,wherein: the processing circuitry of the host computer is configured toexecute a host application; and the UE's processing circuitry isconfigured to execute a client application associated with the hostapplication, thereby providing the user data.

Embodiment 78: The communication system of the previous 4 embodiments,wherein: the processing circuitry of the host computer is configured toexecute a host application, thereby providing request data; and the UE'sprocessing circuitry is configured to execute a client applicationassociated with the host application, thereby providing the user data inresponse to the request data.

Embodiment 79: A method implemented in a communication system includinga host computer, a base station, and a User Equipment, UE, the methodcomprising: at the host computer, receiving user data transmitted to thebase station from the UE, wherein the UE performs any of the steps ofany one of embodiments 1 to 31.

Embodiment 80: The method of the previous embodiment, furthercomprising, at the UE, providing the user data to the base station.

Embodiment 81: The method of the previous 2 embodiments, furthercomprising: at the UE, executing a client application, thereby providingthe user data to be transmitted; and at the host computer, executing ahost application associated with the client application.

Embodiment 82: The method of the previous 3 embodiments, furthercomprising: at the UE, executing a client application; and at the UE,receiving input data to the client application, the input data beingprovided at the host computer by executing a host application associatedwith the client application; wherein the user data to be transmitted isprovided by the client application in response to the input data.

Embodiment 83: A communication system including a host computercomprising a communication interface configured to receive user dataoriginating from a transmission from a User Equipment, UE, to a basestation, wherein the base station comprises a radio interface andprocessing circuitry, the base station's processing circuitry configuredto perform any of the steps of any one of embodiments 32 to 57.

Embodiment 84: The communication system of the previous embodimentfurther including the base station.

Embodiment 85: The communication system of the previous 2 embodiments,further including the UE, wherein the UE is configured to communicatewith the base station.

Embodiment 86: The communication system of the previous 3 embodiments,wherein: the processing circuitry of the host computer is configured toexecute a host application; and the UE is configured to execute a clientapplication associated with the host application, thereby providing theuser data to be received by the host computer.

Embodiment 87: A method implemented in a communication system includinga host computer, a base station, and a User Equipment, UE, the methodcomprising: at the host computer, receiving, from the base station, userdata originating from a transmission which the base station has receivedfrom the UE, wherein the UE performs any of the steps of any one ofembodiments 1 to 31.

Embodiment 88: The method of the previous embodiment, further comprisingat the base station, receiving the user data from the UE.

Embodiment 89: The method of the previous 2 embodiments, furthercomprising at the base station, initiating a transmission of thereceived user data to the host computer.

At least some of the following abbreviations may be used in thisdisclosure. If there is an inconsistency between abbreviations,preference should be given to how it is used above. If listed multipletimes below, the first listing should be preferred over any subsequentlisting(s).

-   -   μs Microsecond    -   3GPP 3rd Generation Partnership Project    -   5G Fifth Generation    -   AP Access Point    -   ASIC Application Specific Integrated Circuit    -   BS Base Station    -   CP Cyclic Prefix    -   CPU Central Processing Unit    -   eNB Enhanced or Evolved Node B    -   FPGA Field Programmable Gate Array    -   GEO Geostationary Orbit    -   GHz Gigahertz    -   gNB New Radio Base Station    -   GPS Global Positioning System    -   ID Identifier    -   IoT Internet of Things    -   km Kilometer    -   LEO Low Earth Orbit    -   LTE Long Term Evolution    -   MEO Medium Earth Orbit    -   MME Mobility Management Entity    -   ms Millisecond    -   Msg1 Message 1    -   Msg2 Message 2    -   Msg3 Message 3    -   Msg4 Message 4    -   MTC Machine Type Communication    -   NGSO Non-Geostationary Orbit    -   NR New Radio    -   NR-PSS New Radio Primary Synchronization Signal    -   NR-SSS New Radio Secondary Synchronization Signal    -   OFDM Orthogonal Frequency Division Multiplexing    -   OFDMA Orthogonal Frequency Division Multiple Access    -   OTT Over-the-Top    -   PBCH Physical Broadcast Channel    -   PDCCH Physical Downlink Control Channel    -   P-GW Packet Data Network Gateway    -   PRACH Physical Random Access Channel    -   PUCCH Physical Uplink Control Channel    -   PUSCH Physical Uplink Share Channel    -   RAN Radio Access Network    -   RAR Random Access Response    -   RA-RNTI Random Access Radio Network Temporary Identifier    -   RAT Radio Access Technology    -   RS Reference Signal    -   SCEF Service Capability Exposure Function    -   SI System Information    -   SIB System Information Block    -   SS Synchronization Signal    -   SSB Synchronization Signals/Physical Broadcast Channel Block    -   TA Timing Advance    -   TR Technical Report    -   UE User Equipment

Those skilled in the art will recognize improvements and modificationsto the embodiments of the present disclosure. All such improvements andmodifications are considered within the scope of the concepts disclosedherein.

REFERENCES

-   [1] TR 38.811, Study on New Radio (NR) to support non-terrestrial    networks-   [2] RP-181370, Study on solutions evaluation for NR to support    non-terrestrial Network

1. A method performed by a wireless device for random access, the methodcomprising: performing an open-loop timing advance estimation procedureto thereby determine an open-loop timing advance estimate for an uplinkbetween the wireless device and a base station; and transmitting arandom access preamble using the open-loop timing advance estimate. 2.The method of claim 1 further comprising: receiving, from the basestation, a random access response comprising a timing advance value; anddetermining a timing advance for the uplink between the wireless deviceand the base station based on the timing advance value comprised in therandom access response and the open-loop timing advance estimate.
 3. Themethod of claim 2 wherein the random access response schedules resourcesfor an uplink transmission from the wireless device, and the methodfurther comprises: transmitting an uplink transmission to the basestation using the scheduled resources and the determined timing advance,the uplink transmission comprising an identity of the wireless deviceand an indication of the open-loop timing advance estimate.
 4. Themethod of claim 3 wherein the indication of the open-loop timing advanceestimate is the open-loop timing advance estimate.
 5. The method ofclaim 3 wherein the indication of the open-loop timing advance estimateis a differential value that equals a difference between the open-looptiming advance estimate and a predefined or preconfigured referencevalue.
 6. The method of claim 1 wherein the random access preamble is afunction of the open-loop timing advance estimate.
 7. The method ofclaim 6 further comprising selecting the random access preamble from asubgroup of a plurality of possibly random access preambles, thesubgroup being chosen based on the open-loop timing advance estimate. 8.The method of claim 6 wherein the random access preamble provides anindication of the open-loop timing advance estimate.
 9. The method ofclaim 6 further comprising: receiving, from the base station, a randomaccess response comprising a timing advance value; and determining atiming advance for the uplink between the wireless device and the basestation based on the timing advance value comprised in the random accessresponse and the open-loop timing advance estimate.
 10. The method ofclaim 9 wherein the random access response schedules resources for anuplink transmission from the wireless device, and the method furthercomprises: transmitting an uplink transmission to the base station usingthe scheduled resources and the determined timing advance, the uplinktransmission comprising an identity of the wireless device andinformation that, together with a random access preamble transmitted bythe wireless device, provide an indication of the open-loop timingadvance estimate.
 11. The method of claim 1 wherein the base station ispart of a satellite radio access network comprising a satellite and agateway that communicatively couples the base station to the satellite.12-42. (canceled)
 43. A method performed by a base station for enablingrandom access in a radio access network, the method comprising:detecting a random access preamble from a wireless device; transmittinga random access response comprising a timing advance value; andreceiving, from the wireless device, an uplink transmission, the uplinktransmission comprising an identity of the wireless device and anindication of an open-loop timing advance estimate utilized by thewireless device to transmit the random access preamble.
 44. The methodof claim 43 wherein the base station is part of a satellite radio accessnetwork comprising a satellite and a gateway that communicativelycouples the base station to the satellite.
 45. A method performed by abase station for enabling random access in a radio access network, themethod comprising: detecting a random access preamble from a wirelessdevice, the random access preamble being a function of an open-looptiming advance estimate of the wireless device; and transmitting, to thewireless device, a random access response comprising a timing advancevalue.
 46. The method of claim 45 wherein the random access preamble isfrom a subgroup of a plurality of possibly random access preambles, thesubgroup being indicative of the open-loop timing advance estimate. 47.The method of claim 45 wherein the random access preamble provides anindication of the open-loop timing advance estimate.
 48. The method ofclaim 45 further comprising: receiving, from the wireless device, anuplink transmission comprising an identity of the wireless device andinformation that, together with the random access preamble transmittedby the wireless device, provide an indication of the open-loop timingadvance estimate.
 49. The method of claim 45 wherein the base station ispart of a satellite radio access network comprising a satellite and agateway that communicatively couples the base station to the satellite.50-76. (canceled)